The present invention relates to a treatment of the water containing manganese, in particular, to a method and an apparatus for treating the water containing high concentration of soluble manganese including an irrigation water, an industrial waste water, a sludge treatment waste water for water supply or the like.
As for a manganese removal method by a fluidized bed, a technology disclosed by JP-A-10-137772 (Japanese Patent Laid-open Publication) is well known and a configuration thereof is shown in FIG. 5.
In the manganese removal method having a configuration shown in FIG. 5, the soluble manganese in the water to be treated is deposited and removed as manganese carbonate by applying a water 11 containing carbonic acid ions or including carbonic acid ions added thereto as an upward flow to a fluidized bed reaction tower 1 with no support bed containing manganese sand therein as a fluidized bed material 2, and by injecting an alkaline material into a vicinity of an inlet port 4 for the water to be treated of the fluidized bed reaction tower or into the fluidized bed so as to adjust a pH value of the water to be treated in the fluidized bed into 8 to 10.
The manganese removal method by the known fluidized bed will be now described in detail.
In a neutral or approximately neutral water, manganese exists in a form of Mn(HCO3) or MnSO4 when it is divalent, and also in other form of MnO2xc2x7mH2O when it is tetravalent. In this case, what is deposited and removed is the divalent manganese which takes a form of ion.
The divalent manganese reacts with carbonic acid ion to produce manganese carbonate as shown in a reaction formula (1).
Mn2++HCO3xe2x88x92+OHxe2x88x92xe2x86x92MnCO3↓+H2Oxe2x80x83xe2x80x83(1)
Manganese carbonate in the water to be treated gradually lowers a solubility thereof as a pH rises and moves into a metastable state, and then is crystallized. At that time, when the manganese carbonate in its metastable state comes in contact with the bed material for deposition, manganese carbonate is deposited on a surface of the bed material. Under this condition, the pH control is important because the deposition does not occur when the pH is low, and more manganese hydroxide rather than manganese carbonate is deposited when the pH is too high.
The conventional method, however, has the problems that, when the water to be treated includes high concentration of manganese, a metastable state period of the manganese becomes shorter and more amount of manganese hydroxide is likely to be deposited, and that, especially in the large treating apparatus, it is difficult to effectively inject arbitrary quantity of alkaline materials into plural portions of the fluidized bed. Further, since manganese existing in the water as a suspended solid has no relation with the above reaction, the suspended manganese in the water cannot be removed by the conventional manganese removal method. Furthermore, the above method has problems that, when a pH value of the water to be treated varies over wide range, a control thereof is difficult, and that, when the water to be treated includes high concentration of manganese, the metastable state of the manganese becomes shorter and more amount of manganese hydroxide is likely to be deposited.
The present invention is achieved in the light of the problems in the prior art described above, and a first object thereof is to provide a method and an apparatus for treating manganese containing water, in which the deposition of manganese hydroxide can be suppressed even if the concentration of manganese is high, and the alkaline material can be injected effectively. Further, a second object of the present invention is to provide a method and an apparatus for treating manganese containing water, in which both of the soluble manganese and the suspended manganese in the water can be removed.
Furthermore, a third object of the present invention is to provide a method and an apparatus for treating manganese containing water, in which the pH variation in the water to be treated can be easily coped with and the generation of manganese hydroxide can be suppressed even if the manganese concentration rises.
In order to accomplish the first object, the present invention provides a treating method of a manganese containing water for crystalizing and removing a soluble manganese in the water by applying the water to be treated containing carbonic acid ions as an upward flow to a fluidized bed reaction tower with no support bed containing manganese sand therein as a fluidized bed material, and by adjusting a pH value of the water to be treated in the fluidized bed, said method characterized in that a plurality of said fluidized bed reaction towers is provided and each of them is connected in series so that the water to be treated flows through them to make a multistage treatment.
Further, the present invention provides a treating apparatus of a manganese containing water,for crystalizing and removing a soluble manganese, comprising a fluidized bed reaction tower with no support bed containing manganese sand therein as a fluidized bed material, an inlet port provided on a bottom portion of said reaction tower for introducing a water to be treated containing carbonic acid ions, an outlet port provided on an upper portion of said reaction tower for discharging the treated water, and an injection port for injecting alkaline material for adjusting a pH value of the water to be treated in the fluidized bed, said apparatus characterized in that a plurality of said fluidized bed reaction towers is provided, and each of them is connected in series and is equipped with the injection port of alkaline material on the bottom portion of the reaction tower near to the inlet port of the water to be treated.
In the method and apparatus described above, it is preferable that the pH value of the water to be treated in the fluidized bed is controlled such that the pH value increases as a stage of the reaction tower proceeds from a former stage to a latter stage among the plurality of reaction towers while keeping a range thereof within 8 to 10, and it is also preferable that a pH control device is provided for controlling the pH value as described above.
In order to accomplish the second object, the present invention provides a treating method of a manganese containing water for crystalizing and removing a soluble manganese in the water by applying the water to be treated containing carbonic acid ions as an upward flow to a fluidized bed reaction tower with no support bed containing manganese sand therein as a fluidized bed material, and by adjusting a pH value of the water to be treated in the fluidized bed, said method characterized in that a suspended manganese in the water to be treated is removed along with the soluble manganese therein by forming, on a manganese sand fluidized bed in said fluidized bed reaction tower, a layer of suspended solid in the water to be treated which has passed through said manganese sand fluidized bed and by removing said layer of suspended solid.
Further, the present invention provides a treating apparatus of a manganese containing water for crystalizing and removing soluble manganese, comprising a fluidized bed reaction tower with no support bed containing manganese sand therein as a fluidized bed material, an inlet port provided on a bottom portion of said reaction tower for introducing a water to be treated containing carbonic acid ions, an outlet port provided on an upper portion of said reaction tower for discharging the treated water, and an injection port for injecting alkaline material for adjusting a pH value of the water to be treated in the fluidized bed, said apparatus characterized in that a suspended solid in the water to be treated is formed into a layer on a manganese sand fluidized bed in said fluidized bed reaction tower, and an ejector pipe is further provided in said layer of suspended solid for ejecting said suspended solid.
In the method and apparatus described above, it is preferable that the pH value of the water to be treated is controlled to be within a range of 8 to 10 by injecting the alkaline material to the bottom portion of the reaction tower near to the inlet port of the water to be treated.
As for the fluidized bed reaction tower, a horizontal cross section thereof in a portion where the suspended solid layer is formed on the manganese sand fluidized bed shall be larger than, preferably 1.4 times or more as large as that in another portion for the manganese sand fluidized bed.
In order to accomplish the third object, the present invention provides a treating method of a manganese containing water for crystalizing and removing a soluble manganese in the water by applying the water to be treated containing carbonic acid ions as an upward flow from a bottom portion of a reaction vessel to said fluidized bed reaction vessel with no support bed containing manganese sand therein as a fluidized bed material, and by injecting alkaline material into the bottom portion of the reaction vessel near to an inlet port of the water to be treated and/or into the fluidized bed to adjust a pH value of the water to be treated in the fluidized bed to be within a range of 8 to 10, said method characterized in that a desired volume of the treated water is introduced into the water to be treated for circulatory use.
Further, the present invention provides a treating apparatus of a manganese containing water for crystalizing and removing a soluble manganese, comprising a fluidized bed reaction vessel with no support bed containing manganese sand therein as a fluidized bed material, an inlet port provided on a bottom portion of said reaction vessel for introducing a water to be treated containing carbonic acid ions, an outlet port provided on an upper portion of said reaction vessel for discharging the treated water, and an injection port provided on the bottom portion of the reaction vessel near to the inlet port of the water to be treated and/or in the fluidized bed to adjust a pH value of the water to be treated in the fluidized bed to be within a range of 8 to 10, said apparatus characterized by further comprising a circulation path connecting said outlet port of the treated water and the inlet port of the water to be treated for circulating a desired quantity of said treated water.
As for the circulation of the treated water in the treating described above, it is preferable that a sedimentation tank is provided on a middle of the circulation path to use a part of supernatant liquid therein.